This is an improvement upon the invention of U.S. Pat. No. 4,179,835 which illustrates a gravity actuated door held in raised position by a trip rod secured between vertical posts on a rearward extension of the trap beyond a back wall. The extension beyond the back wall added to the complexity and cost of traps constructed in accordance with the patent and took up space while subjecting the trap to the danger of accidental dislodgement of the trip rod.
In addition to the foregoing patent, some animal traps are disclosed in U.S. Pat. Nos. 844,517, 1,990,861, 2,038,068, 2,502,836, 2,793,464, and 3,975,857.